This invention relates to materials having very high electrical conductivity. More particularly, it relates to highly conductive materials formed from high molecular weight compounds and techniques for producing such highly conductive materials.
Because electrical conductors play such a fundamental and ubiquitous role in modern technology, improvements in conductors are of obvious importance and utility. In particular, because electrical resistivity in conductive materials results in irreversible dissipation of energy, it is clearly desirable to produce materials having a very high conductivity, especially materials having a very high conductivity at or near room temperatures.
U.S. Pat. No. 5,777,292 granted to the present inventors discloses a new type of material having high conductivity at room temperatures. Because of the unique properties of this conductive material, it would be desirable to improve upon its properties and to provide new and useful applications for it.
Accordingly, the present invention provides improved materials having stable and very high conductivity at room temperatures. In a preferred embodiment, the materials are formed into thin films, membranes, blocks, wires, matrices, aerogels, or other forms. Preferably, the material has an anisotropic electric conductivity, typically in a direction normal to the surface in the case of a membrane or film. The invention also includes various important and useful practical technological applications of these unique materials. Such materials are preferably produced by forming a medium of macromolecular substance, generating free electrons in the medium, inducing these electrons to form electronic channels within the medium, and substantially solidifying the medium to stabilize the positions of the channels. In a preferred embodiment the material substance is a polymer having at least 76.8% single bonds, preferably at least 80% single bonds, and most preferably at least 90% single bonds of all covalent bonds comprising the molecule. In addition, the material has a molecular weight of at least 2 kDa, preferably at least 15 kDa, and most preferably at least 300 kDa. The polymer is preferably a hydrocarbon modified by oxygen such as oxidized atactic polypropylene or oxidized isotactic polyhexene. Alternatively, the polymer is preferably a polyurethane or a polymer such as polydimethylsiloxane which has a silicon-oxygen main chain. A preferred method for producing the material includes forming a thin film of the macromolecular medium and exposing it to UV light in order to assist in the formation of free electrons. The generation of electronic channels within the medium is preferably assisted by one of various enrichment techniques such as heating the medium and exposing it to an electric field, microwaves, or ultrasound. In order to stabilize the positions of the channels to allow reliable conduction through the medium, the preferred method includes a solidification of the medium. Preferably, the solidification is accomplished by cross-linking or by cooling.
The material produced by the invention has stable electronic channels whose room temperature conductivity is preferably greater than 106 S/cm, more preferably greater than 107 S/cm, and most preferably more than 108 S/cm. The material is characterized by a Young""s modulus preferably greater than 0.1 MPa, more preferably greater than 0.2 MPa, and most preferably greater than 1.0 MPa. The material also has an oxygen content preferably between 0.1 atomic % and 13 atomic %, more preferably between 0.2 atomic % and 12.0 atomic %, and most preferably between 0.3 atomic % and 10.0 atomic %. The material preferably has more than 76.8% single bonds, more preferably has more than 80% single bonds, and most preferably has more than 90% single bonds. A static dielectric constant of the material is preferably greater than 2.4, more preferably greater than 3.0, and most preferably greater than 4.0, measured in a direction perpendicular to the surface of the film at about 1000 Hz. In the form of a thin film, the material of the present invention preferably has electrically conductive channels oriented anisotropically in the direction perpendicular to the surface of the film. As a result, the conductivity of the material is also anisotropic.